This invention relates to the art of color coating such edible consumer products as pharmaceutical tablets, confectionary pieces, and the like. More particularly, the invention is directed to a dry pigment composition used for making a color coating suspension. However, the invention also has application to the internal coloring of products, for example, the internal coloring of candy.
The color coating of products can be advantageously accomplished by applying a film forming pigment containing suspension, which typically includes the presence of a film forming polymer. In other cases, the color coating of products is appropriately accomplished by applying a sugar syrup suspension containing an aqueous dispersion of pigment.
The general techniques of film coating and sugar coating are known in the prior art. For example, U.S. Pat. No. 2,954,323 to Endicott et. al. discloses the improved efficiency of the film coating process and the superior coating properties of the products made thereby.
The coating suspensions used in film coating or sugar coating are typically made from commercially available pigment suspensions, which are conventionally concentrated non-aqueous dispersions of lake pigments, usually including a colloid such as polyvinylpyrollidone for maintaining the pigment in dispersion. The pigment dispersions are typically stirred into a larger volume of polymer solution or sugar solution to form the color coating suspensions. Examples of such pigment dispersions and their use are described in U.S. Pat. No. 3,981,984 to Signorino. The U.S. application to Heinze et. al., filed on the same day as this application, discloses an aqueous pigment suspension, including a viscosity lowering agent such as sodium citrate or similar salts of carboxylic acids.
The purpose of the present invention was to obtain a dry composition, rather than a liquid pigment suspension, which could be added directly to a polymer solution or sugar syrup solution to form a color coating suspension. Dry compositions have heretofore not been widely used because of the difficulties involved with their application. Dry compositions have a tendency to agglomerate and resist dispersion in solution. This can result in a poor quality coating, since the coating, in the form of a very thin film, must be uniform and consistent from one batch of tablets to the next. It is desired to obtain a coating exhibiting a smooth, polished, and elegant appearance which requires well dispersed pigment particles. However, this has been difficult to obtain with a dry composition, and the results have been unsatisfactory.
U.K. Patent Application No. GB 2065691A, by Porter et. al., published on July 1, 1981, discloses a method of making a dry film coating composition which comprises the steps of mixing a polymer powder, such as methylcellulose, and pigment particles in a blender, adding a placticizer such as polyethylene glycol to the blender containing the polymer-pigment mix, and mixing until the combined mix is throughly blended. A surfactant or a flow aid is optional.
The present applicant has invented a dry composition for use in film coating or sugar coating, which comprises pigment particles and a small quantity of what is referred to as a dispersing agent, which has an extraordinary effect on the pigment particles. The dispersing agent effects the pigment particles in the dry state as well as facilitating dispersion into solution. The dry composition forms uniform small particles that maintain a striking degree of separation. The particles do not agglomerate, and as a result, a more uniform coating is obtained. The solubility of the composition in the film forming solution increases by a factor of five or more. The phenomenon known as specking, caused by larger sized pigment particles that do not disperse, is rendered insignificant or absent.
The present composition need not contain the high levels of polymer or plasticizer required in U.K. Patent Application No. GB 2065671A, referred to above. The present composition is useful in both aqueous and organic film coating and in sugar coating as well. The composition readily disperses in liquid as a result of the dispersing agent.
The advantage of a dry pigment composition in comparison to a liquid pigment suspension is great. The dry pigment composition would have virtually unlimited stability and storage life. There is no danger of the pigment particles settling out and hardening, as is liable to occur with pigment suspensions. The necessity for preservatives and the danger of microcontamination is reduced or avoided. Since the composition weighs considerably less than the liquid composition, the expense of shipment and the cost of the product is reduced. The presence of inflammable or deleterious organic solvents is obviated.
A primary object of the present invention is to obtain a dry pigment composition capable of use in a film forming solution or sugar solution.
Another object of the present invention is to obtain a dry pigment composition capable of use for the internal coloring of candy such as jelly beans.
Another object of the present invention is to obtain a dry pigment composition which readily disperses in solution.
A further object of the present invention is to obtain a dry pigment composition which does not agglomerate or form clumps or specks in solution.
A further object of the present invention is to obtain a dry pigment composition which exhibits relatively small and uniform particles.
A further object of the present invention is to obtain a dry pigment composition which forms a coating which is smooth and elegant in appearance.
A further object of the present invention is to obtain a dry pigment composition which has high stability and long storage life.
The above and other objects of the present invention will become apparent from a reading of the following detailed description of the invention and the preferred embodiments thereof.